System of space-discharge devices



Jan. 22, 1929. 1,699,711

E. PETERSON SYSTEM OF SPACE DISCHARGE DEVICES Filed March 4, 1924 2 Sheets-Sheet l Jan. 22, 1929. 1 1,699,711

' E. PETERSON SYSTEM OF SPACE DISCHARGE DEVICES Filed March 4, 1924 2 Sheets-Sheet 2 [aye/76 Pew/5047- Ill Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

EUGENE PETERSON, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC GOM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK. i

svsrnm or sracn-mscnancn nnvrcns.

Application filed March 4, 1924. Serial No. 696,766.

This invention relates to systems of space discharge devices. and more particularly to arrangcnwnts including devices of this character that are used to clt'ect modulation.

In systems employing three electrode 'space discharge tubes heretofore proposed for combining electric waves, it has been customary to make use of the distorting effect produced upon the current flowing in the spacepath of the tube caused by the non-linear relation between the potential applied to a control'electrode in this path and the space current;

The present invention, however, provides an arrangement in which modulation is accomplished substantially only in the circuit connected to the control electrode of the tube.

The term modulation as used in this application means the variation of the shape of a wave.

One object of the invention is to combine electric waves substantially only in the input circuit of space discharge tubes.

Another object is to operate a space dis charge device with its control electrode varied in potential alternately positive and negative with respect to the cathode terminal, whereby a plurality of waves may be combined in the current set up in an input circuit of saiddevice.

A further object is to so arrange a space discharge device that positive potentials of only very small value are impressed upon the control electrode thereof to effect modulation in the circuit connected thereto.

A still further object is to impede the current in the input circuit of a space discharge tube so that modulation takes place therein.

An additional object is to match the input impedance of a space discharge tube, whereby electric waves may be combined in an input circuit thereof.

An additional object is to reduce the amount of unmodulated carrier current transmitted from a space discharge tube system arranged to produce grid current modulation.

A feature of this invention relates to a space discharge modulator wherein modula tion is produced in the input circuit thereof.

A further feature relates to a space discharge modulator having an impedance co1nprising a space path of a secondspace dischargetube connected in its input circuit to limit the current from said tube.

A still further feature of the invention is a push-pull organization. of space discharge tubes, which are arranged to combine waves in the input circuit thereof, for suppressing the unmodulated component of carrier current.

An additional feature concerns means to reduce the amount of unmodulated component of carrier current transmitted from a modulator comprisinga conjugate arrangement of circuits for impressing carrier c0mponets upon the modulator input and output circuits in out of phase relation without producing parasitic oscillations or singing.

This invention makes use of the fact that the impedance, to the flow of current in the circuit connected between the cathode and the control electrode'of a space discharge tube, is, in general, large when the potential of the control electrode is negative and is relatively'small when the potential is positive, to thereby effect the combination of waves in this circuit. By maintaining the average potential of the control electrode at the same potential as the cathode terminal and by supplying a plurality of alternating electric waves or wave components to the input circuit connected between this control electrode and the cathode of the tube, the control-electrode to cathode internal impedance. of the tube will be large during the negative half Waves and small during the positive half Waves, whereby the effects of said waves are combined. a

In the present invention, an impedance element is placed in the tube input circuit, whereby for positive half cycles of the impressed waves, a small positive potential is impressed on this electrode and for negative half cycles of the impressed waves the full negative potential is impressed thereon. This result is rought about by adjusting the impedance to a value such that when the current flows through it during positive half cycles of impressed waves substantially the whole drop of potential occurs across the impedance, but during negative half cycles, since no current is flowing, the full input potential is applied between the control electrode and cathode} Since the impedance of the input circuit,

' carrier wave is in excess of about 1% times the frequencies are im resesed upon this input circuit, they will combined therein to form a modulated wave.

- In a common form of space discharge tube, the control electrode takes the form 0 a grid and for this reason the apparatus described above constitutes a grid current modulator.

It is to be understood that this system, which will be described hereinafter in more detail, ma ,be used to combine waves having different c aracteristics to produce a complex wave havin characteristics correspondingto those of eac of the original waves or it may be used to derive a desired component from a complex wave.

. Grid current modulators have an inherent stability of out ut with respect to amplitude fluctuations of t e applied carrier wave. The operation of such modulator has been found to be stable, even though the amplitude of the The hybrid coil has associated with it a balancing network arranged to balance the impedance of the oscillator. The two branch circuits are thus rendered conjugate to prevent the production of parasitic oscillations caused by energy fed back from the output circuit to the input circuit.

In the drawings, various arrangements embodying the invention are illustrated.

Fig. 1 shows a space discharge device having a'resi stance in its input circuit for producmg grid current modulation.

Fig. 2 illustrates a circuit similar to Fig. 1 n which the resistance is replaced by a space d scharge tube. a

F g. 3 shows curves for explaining the operat on of the invention.

F1 4 shows a grid current modulator in which a winding of a transformer connected in the input circuit has its impedance adjusted balance the input impedance of the tube.

Fig. 5 shows the invention applied to adischarge device for combining carrier and signal waves.

Fig. 6 illustrates an arrangement similar to Fig. 5 which includes discharge devices connected in balanced relation.

Fig. 7 illustrates an arrangement in accordance with this invention for reducing the unmodulated component of carrier current.

Fig. 8 illustrates an arrangementsimilar to that of Fig. 7 in which no losses to the modulated output are interposed by the balanced transformer. v

Fig. 9 illustrates an arrangement similar to Figs. 7 and 8 in which a space discharge tube replaces the balanced transformer.

In the various figures ofthe drawings, like reference characters have been used to indicate like parts.

Referring to Fig. 1, a space discharge tube 10. comprises an anode 11, a cathode 12, and a control electrode 13. An input circuit connected between the electrodes 12 and 13 of the tube comprises an impedance represented'by a resistance 14 in series with the secondary windin of the transformer 15. An output circuit is connected to the cathode 12 and anode 11 and includes a space current source 16 herein shown as a battery and also the primar winding of transformer 17.

If a ternating currents having different characteristics are supplied to the primary winding of transformer15, variations of potential corresponding to the variations of current will be impressed upon the control electrode 13 of tube 10. The normal potential of this electrode is zero with respect to the cathode terminal. When alternating currents are thus supplied to transformer 15, the potential of the electrode 13 is caused to vary from positive to negative values, these terms being used, of course, with reference to the cathode terminal potential which is taken as zero potential. Where the cathode itself has a difference of potential between its terminals, the zero reference is taken as the potential of that cathode terminal to which the grid circuit is connected. The input or id circuit may be connected to either catho e terminal, but where the cathode potential difference is large or appreciable relative to the amplitude of the impressed waves it is obvious that a greater grid rectifying action is obtained by connectin the grid circuit to the positive than to t e negative cathode terminal. It is well known that, when the control electrode 13 of tube 10 is negative, the input impedance of the tube, that is the impedance connected between the electrodes 12 and 13, is hi h. Hence, for negative potentials, substantia y no current flows in the tube input circuit and consequently the full potential of the impressed waves is available at the cathode and control electrode.

pedance of the tube to impressed currents is relatively small. Consequently, current will flow in the input circuit of the tube which current produces a drop of potential in the resistance 14. Thus the positive p otential available between the cathode and control electrode of the tube is small. As the posi tive potential of impressed waves increases, the drop of potential in resistance 14. increases accordingly, whereby the positive potential On the other hand, when the control electrode becomes positive, the improduced and the modulated grid' waves are repeated into the anode-cathode circuit" in accordance with the well-known principles of operation of the three-electrode tube.

This current limiting effect is illustrated by the'curves shown in Fig. 3 in which abscissae represent grid potentials and ordinates represent values of plate current. The 'full line curve represents the normal grid potential plate current characteristic of a tube, such as tube 10, with impedance 14 omitted, The dotted portion of the curve represents the effect of theimpedance 14 in limiting the flow of plate current. a It will be noticed that forchanging positive potential of the control electrode 13, the rate of change of plate current is yery small as compared to its rate of change forchanging negative potential, im-

pressed upon this electrode. a

Thus, it is apparent that when they control electrode is positive, the effect of the resistthis circuit to impress a potential varying in a ance 14 is to limit the plate current in the tube. When components of side band and unmodulated carrier frequency are supplied to the input circuit, they will be combined in accordance with the modulating wave upon the control electrode ofthe tube, whereby detection or demodulation is effected in the input circuit.

Referring to Fig. 2, the space discharge tube 10 has connected in its input circuit a second space discharge tube 18 comprising a cathode 19 and an anode 29. The cathode of tube 18 is connected to the cathode of tube 10 and the anodeof tube 18 is connected in series with the secondary winding of transformer 15 to the control electrode 13 of tube 10. The

, leak resistance 20 is connected in shunt to the input circuit of tube 10. The output circuit of this tube which is connected between its plate and cathode includes aresistance 21 shortcircuited'by switch 22 in series with primary winding of transformer 17 and battery 16.

The action of the modulating circuit of Fig. 2 maybe explained as follows: suppose the potential of the grid 13 of tube 10 is made positive with respect to the anode 20 of tube 18.. The grid 13 of tube 10 will then be positive relative to its filament 12 andcurrentwill tend to flow through the circuit. The resistance of the filament-grid pathin the tube will drop correspondingly. On the other hand the resistance of the filament anode path of tube 18 remains high since the filament is positive with respect to the anode. The potential will then divide accordin to the respective resistance of tube 10 andt e shunt circuit comprism .eai: resistance 20 on-one hand and tube 18 on the other. The net result is that almost theentire impressed voltage is in effect applied across that tube whose grid is madenegative. The leak resistance 20 is inserted to prevent accumulation of a negative charge on the grid of tube 10 and anode 20 of tube 18.

The limitation of space'current may be regulated by changing the battery 16 or by including the resistance 21 in the plate circuit by ppening switch 22. It is'apparent, by reference to the curves ,of Fig. 3, that if the cut off is caused to occurabove the knee of the full line curve, for negative voltages on the con trol electrodes, the relation between control electrode voltage and anode current will be non-linear. In this instance modulation will waves will bear a substantially linear relation to the input waves when the amplitudes are small enough to be confined to the linear part of the characteristic curve, but will bear a non-linear relation to the input waves for greater amplitudes. This means that for small input amplitudes'there will be no modulation produced in the anode circuit, but the modulation will be confined to the grid cir cuit. Even where the amplitudesof the input waves would be sufficient to sweep over the curved portion of a given tube characteristic such as that of'Fig. 3, modulation could be reduced or prevented by including a resistance such as resistance-21in the plate circuit, this resistance being large enough to have the effect of straightening out the tube characteristic or in effect changing to a new characteristic. Thus, it is seen that by designing resisttrol the relative phases 'of the grid'current' and anode current modulation products, so

that these products may be supplied additively to a common load circuit.

The effect of tube 18 in limitin e current in the anode circuit of tube 10 is illi strated by the straight line portion of the curve of Fig.- 3 on the right-hand side of the zero axis. This indicates that the cut-off of plate current in this instance is much more abrupt than when the resistance 14, as shown in Fig. 1, is used.

In Fig. 4: a modulator 30 is connected in tandem to an amplifier 35. The amplifier 35 comprises the three-electrode space discharge tube 36 having an input'circuit including the 1 high shunt impedance to currents within the .frequency band to be transmitted. The imsecondary winding of the transformer 37 and a resistance 38 in series connected between its cathode and control electrode. The output circuit including the-primary of'the transformer 39 in series with a battery 40, extends from the cathode to the anode of tube 36.

Modulator 30 comprises a three-electrode space discharge tube 41 cuit connected between its cathode "and control electrode, and an output circuit connected between its cathode and anode. .The input circuit includes the secondary winding of transformer 39, the impedance of which is such as to match the tube input impedance for alternating current when the control electrode is negative. The output circuit includes the primary windin of an output transformer 42. The secondary winding of transformer 42 has its terminals connected to a band pass filter 43 designed to have a very low shunt impedance to currents of frequencies outside of the transmitted band and a pedance of this filter within the transmitted band may be such as to match the tube output impedance.

' In the operation of the circuit shown in Fig. 4, waves of signal frequencies are transferred by the transformer 37 to the input circuit ofthe amplifier 35. These waves are amplified by amplifier 35 in a manner now well understood and impressed on the input circuit of tube 41. Modulation is effected by the variable input impedance of the tube,

which results when the control electrode goes positive and negative during different parts of the cycles of the impressed waves. lVhen the grid is driven positive the input impedance of the tube drops to a comparatively-low value, while, during the time that the grid is driven negative, the input impedance is very high and is almost entirely capacitive, being, therefore, dependent upon frequency.

The input impedance of the tube is dependent upon theimpedance of the load connected to the output circuit.

By insertin an impedance of appropriate value as described in connection with the precedin figures in the control electrode circuit the greater part of the potential drop can be made to take place across this external impedance when the control electrode is driven positive while during ,the negative part of the cycle the potential may divide equally across the tube and the external impedance.

Although the external impedance may take the form of a resistance or an inductance, it has been found convenient to have theimpedance of the secondary winding of transformer 39 serve as the external impedance, thus avoiding the introduction of additional losses in the control electrode circuit. The ratio of transformer 39 is preferably made such that having an input c1r-.

and the same impedance relations should obtain in this circuit as in the ordinary power amplifier, that is, the external impedance should be made equal to the internal output impedance of the tube. This is accomplished by proper design of filter 43 which is of the general type disclosed in Patent No. 1,227,113 to Campbellfissued May 22, 1917.

The load impedance in the anode circuit has a material effect upon the input impedance of the tube when the control electrode is negative. hen the load impedance is zero the input impedance of the tube is at its greatest value and when the load impedance is infinite the input impedance of the tube is least. Thus, the impedance of the load cir-- cuit connected to the anode circuit of the tube 41 determines the transformation ratio of the transformer 39 to be used in its input circuit.

The arrangement of the amplifier 35 between the modulator 30 and the input circuit connected to the transformer 37 produces a stabilizing elfect upon the impedance of the modulator circuit as a whole with respect to the line to which its input may be connected. The impedance of the secondary winding of the transformer 39 should preferably match the input impedance of tube 41 when the load circuit of the tube lcomprises the band pass filter 43. This filteris designed to have low shunt impedance for currents of frequencies outside the transmitted band, particularly to the band of signal frequencies and to the carrier frequency but to have high shunt impedance'for currents within the frequency band to be transmitted. Thus, the input impedance of the tube 41 has a high value at carrier and signal frequencies and the corresponding voltages applied to the control electrode of this tube are therefore large, when the input transformer is given the high ratio required to match the input tube impedance as described above.

On the other hand,it maybe more desirable to obtain the maximum advantage from the anode circuit as an amplifying device selective to the modulated wave. It is obvious, that, to do this, provision must be made for reducing to a negligible amount the flow of all currents in the anode circuit exoutput impedance'of tube 4-1 for frequencies within tl f transmitted band. The entire power which tube 41 draws from battery '10 is by this means delivered to the frequency band to be transmitted.

In the system shown in Fig. 5 modulated 'arricr waves are produced by combining 'ares from signalsource 51 with carrier arms from source 52. The sources of waves 51 and 52am connected to a common circuit coupled to the input circuitof a modulator by a transformer 54. The signal source 51 is connected to the common circuit through a transformer 53. The common circuit also comprises a low pass filter LPF which has its input terminals connected to the secondary winding of transformer 53 and a high pass litter llPF which has its input terminals connected to the carrier current source 52. Filters LP] and HPF may be of the genral type disclosed in Patent 1,227,113 to George A. Campbell, issued May 22, 1917. The output circuits of filters LPF and TIFF are connected in series with the primary winding of transformer 54. Filter LPF is arranged to freely pass without substantial attenuation, all currents having frequencies within the range of signals supplied by source 51, and to attenuate currents of frequencies above this range and especially current of the frequency produced by. source 52. High pass filter l-[PF is arranged to pass currents having frequencies within a given hand in which is included the frequency of source 52 and to attenuate currents of frequencies below this band and especially currents of the frequencies reduced by signal source 51. The secondiiiry winding of transformer 54 is connected in the input circuit of a space dischargetube 55, which circuit is connected to a control electrode and cathode of the tube. The input circuit includes a filter F which maybe of the general type described by G. A. Campbell in Patent 1,227.113, issued May 22, 1017. Tube 55 has an output circuit connected to its cathode and anode which includes the pri:

mary winding of an output transformer 56 in series with a space current battery 57. The secondary wmdlnnof transformer 56 may be connected to a power amplifier supplying a signal modulated wave to an an- (ill ' tube 55.

tenna, or it. may be connected to a transmission circuit such as a wire line.

Modulator 50 is arranged to operate in accordance with the principles already set forth wherein modulation is effected in the circuit connected to the control electrode of The secondary Winding of trans former 54 which isincluded in 'this circuit may perform a function similar to the secondary winding of transformer 39 in Fig. 4:. However, it has been found for certain frequencies of the carrier and signal currents, that the impedance of the transformer windin is a. function of frequency. To make the voltage of the waves impressed by sources 51 and 52 upon the control electrode during the negative peaks as large as po'ssible,'the tube impedance should be matched by the transformer and to cutoff the positive peaks most effectively the impedance of the external circuit to these waves should be as large as possible. It is also necessary that thecxternal impedance of the control electrode circuit between the cathode and grid should be very large for the frequency components produced by modulation, that is, the side band frequenc The variable impedance of the trans ormer winding to low fre uencies may result in poorer transmission of t 10' side band at 100 cycles, for example, than at 2,000 cycles and will tend to produce distortion of the signals. In order to make uniform'the impedance of the control electrode circuit to the side band frequencies, the filter F is provided which is designed to have the re uisite impedance to the side band frequencles, but to pass the signal frequency waves and the carrier frequency waves from sources 51 and 52. In order that the voltage impressed upon the control electrode of tube 55 by waves from sources 51 and 52 may be as large as possible, the impedance of the filter F to these waves is made large to match the tube impedance.

In Fig. 0 is shown a-push-pull arrangement of grid circuit modulators in which threeelect rode space discharge tubes 61 and 62 have their in at circuits respectively extending from them cathodes to their control electrodes symmetrically connected with reference to carrier and signal sources, a lead 63 eonmionto both input circuits includes the secondary winding of transformer 64, the primary winding of which may be connected to a source of carrier Waves. One terminal of the lead 63 is connected to a pointintermediate to the cathodes of tubes 01. and 2 and'the opposite terminal of this lead is connected to the midpoint of a secondary winding of transformer 65. the outer terminals of which are.

respectively connected to the control electrodes of tubes 61 and 02 in series with resistances 00 and 67. The primary windingof t ansformer 65 is connected to a source of signal currents. Tubes 61 and 02 have balanced output circuits connected to the cathodes and an odes respectively thereof and including theprimary winding of a transformer 68. The balanced output circuits comprise a common lead extending from the cathodes to the midpoint of the primary winding of the transformer 68, a battery 69 being includedtherm in. The secondary winding of transformer 68 is provided with terminals arranged to be connected to a transmission line or'receiving device.

The operation of the circuit of Fig. 6 is, so far as the differential connection of the tube output circuits is concerned, similar to that describedin Patent 1,343,307, issued to J. R. Carson, June 15, 1920. As in the case of the Carson modulator referred to, one purpose ofthis push-pull arrangement is to suppress in the output circuits of tubes 61 and 62 the unmodulated component of carrier frequencies. However, the modulatingaction of the circuit of Fig. 6 differs from that of the Carson patent in that in the present circuit the modulation products are produced in the grid circuits of the tubes 61 and 62 and are reproduced in the anode-cathode circuits by the controlling. effect of the grid potentials on the anode currents. the other hand, the input waves are repeated into the anode-cathode circuits and the modulation products first appear in the. anodecathode circuits as-a result of the non-linear relation between grid potential and anode current. The resistances 66 and 67 function in the same manner as resistance 17 of-Fig. 1. In Fig. 7 a modulator M, which may be similar to the one described in connection with Fig. 5, is arranged to be supplied with signal frequency waves by the transformer 71 and with carrier frequency waves from a source 72 through a differential potentiometer 73. The output circuit of modulator M is coupled by transformer 7 4 to one winding of a alanced transformer or hybrid coil 75. The output terminals of transformer 75 are connected to the input terminal of a filter 76 also having its output terminals connected, for example, to a wire line or a receiving system, a power amplifier, etc. .A balancing impedance or artificial line 77 is connected to the opposite terminals of transformer 75 and is designed to have impedance characteristics similar to the combined impedance of the filter 7 6 and .wire line or other apparatus connected'to the filter. The midpoints of windings 78 and 79 oftransformer 5 are connected to one half of differential potentiometer 73, whereby an unmodulated wave of the carrier frequency may be impressed upon these windings. Connection is preferably so made that the component of carrier frequency impressed directly from.

the source 72 upon the hybrid coil 75 is in out of phase relation with the component impressed by way of modulator M whereby the latter component is substantially reduced in amplitude.

In Fig. 8 isshown a slightly different circuit arranged to function similar to the Circuit of Fig. 7. In the circuit here shown the source of carrier waves 72 is connected directly to the windings7 8 and 79 of hybrid coil 75 and an artificial network N is pro- In the Carson patent, on.

windings 78 and 79,an unmodulated component of the' carrier frequency of suitable amplitude is impressed upon the output circuit of tube 80. The circuit including the network 83 and transformer 82 is so arranged that waves of the carrier frequency impressed on the output circuit are in out of phase relation with wayes produced therein by the action of modulator 80, whereby the amplitude of waves ofthe carrier frequency in this circuit. is substantially reduced. A transformer 84 is'provided to transmit signal modulated currents from the-output circuit.

In Fig; 9 ananxiliary tube 85 is arranged to perform a function similar to that of the balanced transformer or hybrid coil 75 in Figs. 7 and 8. Tubes and are connected 'to a source of carrier waves 72 so that the carrier current through auxiliary tube 85 opposes to a greater or lesser degree, thecarrier current output from the demodulator 80 without affecting the side band output. By movement of the adjustable contacts on resistance 86 differentially connected to the input circuits of tubes 80 and 85, any degree of opposition may be secured. Modulating current is supplied to the input circuits of tubes 80 and 85 by means of transformer 860.

The arrangements shown in Figs. 8 and 9 are applicable to modulators operating in accordance with the principles set forth herein, that is utilizing grid effects, but are not applicable to the type of modulation heretofore proposed utilizin space discharge tubes since in such modu ators a. component of carrier frequency is required in the anode circuit to produce modulated Waves, that is side band fre uencies.

Although t is invention has been described in connection with certain specific embodiments, it is apparent that the principles herein disclo sed are susceptible of numerous other applications without departing from its,

scope. It is intended, therefore, that this invention is to be limited only by the scope of the appended claims.

What is claimed is i 1. In a modulator, a space dischar e tubehaving a cathode, an anode, and a control electrode, an input'circuit connected to said cathode and control electrode, means for impressing waves of a plurality of frequencies nee upon a circuit connected between said cathode and control electrode, and means including a space discharge path from said cathode to said control electrode to cause said waves to produce in saidicircuit current components representing the combination products of said impressed waves.

2. In a modulating system, a three-electrode space discharge tube, an input circuit connected to two electrodes of said tube,uan output circuit connected to one of said ,two electrodes and a third electrode of said tube, means for supplyingwaves to said input circuit, at least one ofsaid waves being of complex form, and means including a space discharge path between the electrodes connected to said input circuit for producing under control of said waves currents in said input circuit representing the combination products betweensaid supplied waves.

3. A modulator which comprises-a space discharge tube having a cathode, an anode, I

and a grid electrode, an output circuit between. said anode and cathode, sources of high frequency waves and low frequency waves connected to said grid and cathode, and means in circuit with said sources and said grid and cathode for producing current flow in said grid-cathode circuit such that the potential between said grid and cathode corresponds to said high frequency wave varying in amplitude injaccordance with said low frequency wave whereby correspondingly varying waves are repeated in said output circuit, said means including a space discharge path between said grid and cathode.

4. An electric system comprising a threeelectrode space discharge device, input and output circuits therefor, means for supplying waves having different characteristics to said input circuit, and means included in said input circuit for efiecting modulation of one of said waves by another of said waves, said last means comprising an impedance in the ,input circuit of such'magnitude that most of the potential drop produced by currentflow in the input circuit resulting from application of said waves occurs across said impedance.

5. In a modulator, a space discharge tube having an input circuit and an output circuit, each of said circuits including a space discharge path through said tube,'and means for causing modulation to be produced within said tube in both of said circuits.

' 6. The method of modulating alternating current of one frequency in accordance with alternating current of a diiierent frequency by means of a space discharge device having input and output circuitswhich comprises impressing currents and voltages of both frequencies upon an input circuit of large impedance, thereby controlling the amplitude of one of the half cycles of currents so that substantial modulation results in the input circuit, and the modulated component is repeated in amplified form in the output circuit. v

7. The method of combining alternating currents having different characteristics by means of a space discharge device having an input circuit associated therewith which comprises supplying said alternating currents of different characteristics to said input cir-- cuit, and impeding the respective half cycles of the alternating currents differently in said input circuit.

8. The method of combining alternating currents having different "characteristics by means of a space discharge device having an input circuitassociated therewith which comprises supplying said alternating currents of different characteristics to said input circuit, and substantially suppressing in said input circuit, one half of each cycle of the alternating currents.

9. A wave combining circuit comprising a space discharge device having cathode, anode and grid or impedance-controlling elen'lents, an input circuit associated with said grid and cathode, means to impress on said input circuit waves of a plurality of components to be combined, said input circuit including sufficient impedance to cause the production in said input circuit of current. components representing the combination products of the impressed wave components, and a circuit as-' sociated with the anode and cathode for utilizing the combination pro-ducts set uptherein from said input circuit.

10. A wave combining circuit comprising a space discharge device, having cathode, anode and control elements, means for apply- .ing to the cathodecontrol-elemcnt circuit of said device waves of diflerent components to be combined, means also included between said cathode and control elemen s situated to divide the potential of said different .wave components between itself and the cathodecontrolelement space of said device in a. nonlinear relation whereby combination components between the impressed waves are applied to said cathode and control elements, and a utilization circuit for the combination components as ociated with said cathode and anode,

11. A wave combining circuit comprising a space discharge device having cathode, anode and grid or impedance-controlling elements, an anode-cathode circuit, circuit means to in'ipress across the grid and cathode a plurality of waves to be combined, said circuit means including series impedance whereby said waves set up current-flow through said impedance and also vary the potential of said grid alternately positive and negative with respect to the cathode, said impedance being of sufficient magnitude to make the po- 12. A wavc-comlumng circuit comprising a space discharge device having a cathode, an

anode, a grid or impedancecontrol-element, and means to supply space current between the anode and cathode, an output circuitconnected to the anode and cathode, a circuit for impressing across the grid and cathode voltage components representing the waves to be combined, the connections from the grid to the cathode maintaining the grid at an average potential such as to allow the impressed voltages to drive the grid potential positive and negative with respect to the cathode, said circuit connected across the grid and cathode containing sutiicient impedance to cause the production in the grid-cathode circuit of ourrent-components representing the combination products of the impressed waves, whereby said products are repeated into said output circuit.

13. A wave combining circuit com rising a space discharge device having cathor e, anode and grid or impedance-control elements,an input circuit associated with the grid and cathode, an output circuit associated. with the anode and cathode, means to set up in said input circuit. current flow restricted to the halt waves of one signof a plurality of waves to be combined, and a dissipative impedance associated with said input circuit in the path of flow of said half waves of current whereby the potential drop across said impedance accompanying such currentfiow is applied to said grid, and a utilization circuit for the combination components of said waves connected to said output circuit.

14:. The method of employing a space discharge device of the an anode and a grid or impedance-control element to combine Waves of different characteristics, comprising utilizing the rectifying property of the grid-cathode internal impedance of the device to confine current flow in an external .grid cathode circuit to half waves of one sign in the case of all of the applied waves, developing in said external circuit a potential drop proportional to the said currents in such direction as to lower the average grid-cathode voltage producing such rectification, and utilizing the resultant gridcathode potential to control the flow of space current in an external anode-cathode circuit associated with said device.

15. The method of operating a space dlstype having a cathode,

charge device of the type having cathode, anode and grid elements, to combine waves of different frequencies, which comprises the steps of applying the half waves of potential of one sign across the grid and cathode of said device and causing the half waves of opposite sign to produce current flow through a dissipative impedance associated with said device such that the accompanying drop of potential through said impedance isv applied to the grid superposed on the half waves of potential, and utilizing the resulting gridto-cathode potentials to control the flow of current in an external circuit associated with the anode and cathode.

16. A wave combining circuit comprising a pair of space discharge devices each having cathode, anode and grid or impedance-controlling elements, an input circuit having a portion common to the cathodes and portions individual to the grids of said devices, impedance means in the portions individual to the grids, and means for impressing on said input circuit a plurality of waves to be combined, such that said waves drive the potentials of said gridspositive and negative with respect to the cathodes and produce in the individual portions of the input circuit current components representing the combination products of the impressed waves, such components being of respectively opposite phase in the two individual input circuit portions, and other components in the same phase in said individual circuit portions, and an outgoing circuit differentially associated with said anodes and cathodes whereby the combination products are repeated into said outgoing circuit while the other mentioned components of like phase are suppressed in said outgoing circuit.

17.'A wave combining circuit comprising a pair of space discharge devices each having cathode, anode and grid or impedance controlling elements, a dividcd input circuitv havmg a central branch common to said cathodes and outer branches individual to said grids,

a source of waves difierentially associated with said outer branches, a second source of waves associated with said central branch, impcdances in said outer branches of sutficient magniture to produce current components in said branches representing the combination products of waves from said two sources, and an outgoing circuit di ii'erentiall y associated with said anodes and cathodes.

In witness whereof, I hereunto subscribe my name this 29th day of Februarv A. D. [924.

EUGENE PETERSON. 

